To save everything in cmd windows as a txt file,
dir > t.txt
You cannot see anything in the screen, but everything supposed to be displayed saved in t.txt file.
It calls "output redirection".
If you want to print out,
dir > prn
We can utilize this skill for java with compiled program (e.g., double_data.class).
e.g., in cmd windows,
java double_data > t.txt